The invention relates to a method of operating an absorption heat pump or refrigerator, consisting at least of a refrigerant circuit and a refrigerant-containing solution circuit, with a generator for evaporating refrigerant from the solution with the supply of relatively high-temperature heat, a condenser for condensing refrigerant and giving up heat at an intermediate temperature level, an evaporator for evaporating refrigerant with the absorption of heat from a relatively cold heat source, a heat exchanger for transferring heat from the liquid passing out of the condenser to the refrigerant vapour and liquid coming from the evaporator, an absorber for absorbing refrigerant vapour into the solution with the giving-up of heat at an intermediate temperature level, and means for circulating the solution or maintaining the pressure.
A method of this kind is known from Plank, R., "Handbuch der Kaltetechnik" (1959), Part VII, particularly pages 10 to 19. In the apparatus described there a heat exchanger, also referred to as an after-cooler, afterevaporator, or liquid cooler, can be included, in which condensate coming from the condeners is cooled by heating vapour and evaporating any entrained liquid. The action of this heat exchanger is described on page 13 and on pages 182 to 188 in the work referred to above. In an apparatus of the type first described above it is desired to achieve optimising regulation of the refrigerant flow (D.sub.exp) via a throttle means to the evaporator in order to improve the performance of the apparatus. In the case of a heat pump the performance is measured by the heating effect output for a constant energy input, and in the case of a refrigerator the refrigerating effect for a constant generator power.